But did you know that dolphins and porpoises, which are far smaller and look quite different, are also types of specialized whales? Today, there about 80 species of living whales, or cetaceans.

These 80 species fall into two groups: baleen and toothed.

A type of baleen whale, humpback whales reach up to 50 feet long.

Talia Romito and Sophie Webb/Courtesy of NOAA

Called mysticetes—a word derived from the Greek for “mustache” and “whales”—baleen whales are toothless. They feed by using their unique baleen—fringes of keratin hanging from the roof of their mouths—to help keep vast numbers of tiny prey (such as krill) in and filter water out. Blue whales, humpback whales, and gray whales are all mysticetes.

Baleen whales, including the Bryde's whale pictured here, have two blowholes through which they breathe. Toothed whales have only one.

Isabel Beasley/Courtesy of NOAA

Called odontocetes—from the Greek for “toothed whales”—toothed whales are the bigger group, comprising about 70 of the whale species living today. The group includes beaked whales and sperm whales. (Sperm whales are far larger than most other species in this group—reaching about 60 feet long.)